1. Field of the Invention
The present invention relates to an improved light emitting device which comprises a group III nitride compound semiconductor satisfying the formula Al.sub.X In.sub.Y Ga.sub.1-X-Y N, inclusive of X=0, Y=0, X=Y=0. The light emitting semiconductor device is applicable to light-emitting diodes or laser diodes.
2. Description of Related Art.
A light emitting device using compound semiconductors includes one which emits visible light with short wavelength. In particular, the group III nitride compound semiconductors have recently attracted a large amount of attention because they have high efficiency since they are a direct transition type. Moreover, the group III nitride compound semiconductors have attracted attention because they emit a blue light which is one of three primary colors of lights.
Regarding such a light emitting device, a blue light emitting diode with a double-hetero structure is known in which a first semiconductor layer comprising an n-conductive type semiconductor, an emission layer and a second semiconductor layer comprising a p-conductive type semiconductor are layered, in order, on a sapphire substrate. In the light emitting diode, a transparent electrode made of gold is formed by evaporation on substantially the entire surface of the second semiconductor layer which is a p-conductive type. A second pad electrode made of gold is attached on the transparent electrode. A first pad electrode made of aluminum is directly attached on the first semiconductor layer.
The blue light emitting diode comprising a group III nitride compound semiconductor is sensitive to static electricity. That is, the blue light emitting diode can withstand several hundreds of volts (400.about.500 volts) in forward static electricity whereas it can withstand only a few dozens of volts (30.about.50 volts) in reverse static electricity. For example, static electricity having a voltage over what the reverse static electricity can withstand is charged on the human body. When the static electricity of the human body is applied to the blue light emitting diode in the reverse direction, damage or a breakdown may occur in the diode. The blue light emitting diode is, thus, very sensitive or difficult to handle.